Flexible skirts for surface effect devices



Feb. 20, 1968 J. H. BERTIN FLEXIBLE SKIRTS FOR SURFACE EFFECT DEVICES 2 Sheets-Sheet 1 Filed April 19, 1965 117mm jean Henri Ber fuorneys J. H. BERTIN FLEXIBLE SKIRTS FOR SURFACE EFFECT DEVICES Feb. 20, 1968 Filed April 19, 1965 2 Sheets-Sheet 2 Im/en m' Tedd 1 Henr/ Bevan 8 9 77/Mlw fiizarneys Unite States Patent 11 Claims. (l. 180127) It has already been proposed to support ground effect platforms or like vehicles by means of a plurality of independently supplied fluid cushions bounded by flexible skirts, the latter being preferably of circular platform, where there is absence of mutual contact between them, and of conical side elevation, which conferred upon them a stable form due to the internal fluid cushion associated to each skirt. In some cases, an overall peripheral skirt is used to surround the unit skirts.

Tests conducted with such platforms have revealed the value of utilizing the largest possible part of the vehicle area for imparting lift, and it is the principal object of the present invention to fulfill this desirable requirement.

Considering the skirts made of a flexible material which are secured at their upper edge only and are free everywhere else, their lower edge has a natural tendency to assume the shape of a circle, especially under the effect of the pressure of the air delivered into the skirt by the compressed air source utilized for creating the air cushion.

According to the invention, the plan view of the upper edge of the skirts is given the shape of a regular polygon, for instance a square, having a larger surface than that of the circle formed by the lower edge. The apothem of the polygon or the half length of the side of the square is, however, preferably slightly less than the radius of said circle, whereby to leave, between the lower edges of two substantially tangential skirts, a free space for more easily securing the upper edges of the skirts to the platform structure,

It should be noted that the polygonal or square shape of the upper edge and the strain which results therefrom in the upper part of the skirt, whose cross section progressively merges from this square form into the circular shape of the lower edge, cooperate in providing the vertical stability of the skirts.

Skirts of this type can be arranged on the surface which is to hear them, for instance on the undersurface of a vehicle platform, so as to cover as much as possible of this surface and thus create a large number of separate chambers corresponding to as many unit air cushions. If these cushions are supplied with compressed air independently of each other, local perturbations, for instance asperities of the ground in the case of a vehicle, will cause the pressure to drop in only some of the unit cushions, whereby the device will have a much more uniform action than that of a single cushion which would occupy the whole volume.

When the several skirts are placed against one another their contacting surfaces become deformed and tend to assume a flat shape in the contact zone. According to a feature of this invention one or more flat portions destined to constitute the contact zone or zones with the adjoining skirt or skirts are provided beforehand on the individual skirts.

The following description, which refers to the accompanying drawings, which are given by way of a nonlimitating example, will explain the several objects of the invention and how the same can be carried into practice.

FIGURES 1 and 2 are schematic side elevation and underneath views, respectively, of a unit flexible skirt devoid of any surface in contact with the adjacent skirts.

3,359,623 Patented Feb. 20, 1968 FIGURE 3 shows the skirt of FIGURES l and 2 in developed form.

FIGURE 4 is an alternative constructional'form to FIGURE 1, showing in schematic side elevation two unit flexible skirts in mutual contact.

FIGURE 5 is a corresponding perspective view as seen from above.

FIGURE 6 shows the skirt of FIGURE 5 in developed form.

FIGURE 7 is a schematic view of four adjoining skirts seen from the side of their free edge.

Referring first to FIGURES 1 to 3, there is shown thereon a unit flexible skirt 2 devoid of any common surface of contact with its companion skirts but occupying on the lower surface of a platform 1 having therethrough air supply orifices 1a for the cushions, the largest possible part of this surface between the neighbouring skirts due allowance being made for the gaps which may be necessitated by the members 3 for securing said skirt and the likes thereof to the platform 1 and by the mechanically resistant structural members of the latter.

In plan view, the lower edge 6 of said skirt is circular, while its upper edge 7 is square. The area of the square is greater than that of the circle in order to ensure vertical stability of the skirt, but the length of each side of the square is preferably slightly less than the diameter of the circle whereby to provide space for the securing members 3 between adjacent unit skirts having substantially tangential circular lower edges.

The skirt shown laid flat in FIGURE 3 is composed of alternating triangular surfaces 2a and 2b.

The portions 2a are conical and have a common apex 0 and their lower limit 6 is a circle. The portions 21) are substantially flat and their upper limit 7 is a straight line. The common limits of said portions are in general arcs of hyperbolae but they do not coincide when the skirt has been laid flat.

In a modification, FIGURES 4 to 6, a unit skirt can be so near its neighbor that they are in contact over a flat surface perpendicular to the platform 1. It has moreover been assumed that the triangular surfaces 2a which constitute such a skirt belong to four cones having a common circular base and apices near those of the square formed, in the plane of the upper edge of the skirt, by the members 3 provided for securing this skirt. The contact area 2e is bounded laterally by two hyperbolic arcs 55 and upwardly by a substantially horizontal straight line 5' as shown in FIGURE 5.

This contact area 2e replaces, below this straight line 5, a large part of the surface of a rectilinear-sided triangle 2b and penetrates int o the surfaces of the two adjacent curvilinear sided triangles 2a. In the developed curve of FIGURE 6 this curve 5 separates from the curve 5a which limits the neighbouring developed curvilinear sided triangles.

In FIGURE 7 each of the four associated skirts 1' 1' jg, has two flat faces 2e, 2e serving to aflix each of them against the two neighbouring skirts. In the flat portions e the wall may be twofold and be comprised of the walls of the two adjoining skirts, aflixed against each other and pressed against each other by the pressure of the fluid delivered into the skirts but the Wall could also have one thickness only, the flat portion being then common to the two skirts.

Of course, the invention is not limited to the described embodiment-s but extends to everything that can be obtained when employing technical equivalents.

The skirts may comprise several folds or walls s'ituated one inside the other.

The plan view of the upper edge of the skirts may be a polygon other than a square, for instance a rectangle or a hexagon.

The invention is of course also applicable to supports other than. the platforms or vehicles in which a sustaining fluid is used, especially to hearing and abutments.

What is claimed is:

1. A fluid-cushion skirt made of thin :fiexible material and designed for being fitted at one end thereof to a body of the ground eifect type movable along a bearing surface, with its other end extending freely opposite said surface, wherein said one end of said skirt has a crosssection in the geometric form of at least a part of a polygon whereas said other end of said skirt has a crosssection in the geometric form of at least a part of a circle, the cross-sectional area of said polygonal end being larger than that of said circular end and the shape of said skirt evolving longitudinally from said polygonal end to said circular end.

2. Skirt as claimed in claim 1, wherein the cross-sectional area of said skirt gradually decreases from said polygonal end to said circular end.

-3. Skirt as claimed in claim 1, wherein said polygonal end is in the general form of a square.

4. Skirt as claimed in claim 3, wherein the diameter of said circular end is greater than the distancebetween opposite sides of said polygonal end.

5. Skirt as claimed in claim =1, further comprising at least one substantially fiat, generally longitudinal side portion.

6. A ground effect vehicle or like body movable along a bearing surface in spaced relationship therewith, comprising at least one fluid-cushion skirt made of thin flexible material and fitted at one end thereof to said body with the other end thereof extending freely opposite said surface, wherein said one end of said skirt has a crosssection in the geometric form of at lea-st a part of a polygon whereas said other end of said skirt has a cross-section in the geometric form of at least a part of a circle, the cross-sectional area of said polygonal end being larger than that of said circular end and the shape of said skirt evolving longitudinally from said polygonal end to said circular end.

7. Body as claimed in claim 6, wherein the cross-sectional area ofsaid skirt gradually decreases from said polygonal end to said circular end.

8. Body as claimed in claim 6, wherein said polygonal end is in the general form of a square.

'9. Body as claimed in claim 8, wherein the diameter of said circular end is greater than the distance between opposite sides of said polygonal end.

10. Body as claimed in claim 6, comprising a plurality of similar skirts positioned adjacent each other with the edges of their polygonal ends in close juxtaposition.

11. Body as claimed in claim 10, wherein adjacent skirts each comprise at least one substantially flat, generally longitudinal side portion.

References Cited UNITED STATES PATENTS 3,180,443 4/1965 Jones 7 3,247,921 2/ 1966 Latimer-Needham et al. 1807 3,251,432 5/1966 Fischer et al. 1807 OTHER REFERENCES Science and Mechanics, June 1960, page 4.

A. HARRY LEVY, Primary Examiner. 

1. A FLUID-CUSHION SKIRT MADE OF THIN FLEXIBLE MATERIAL AND DESIGNED FOR BEING FITTED AT ONE END THEREOF TO A BODY OF THE GROUND EFFECT TYPE MOVABLE ALONG A BEARING SURFACE, WITH ITS OTHER END EXTENDING FREELY OPPOSITE SAID SURFACE, WHEREIN SAID ONE END OF SAID SKIRT HAS A CROSSSECTION IN THE GEOMETRIC FORM OF AT LEAST A PART OF A POLYGON WHEREAS SAID OTHER END OF SAID SKIRT HAS A CROSSSECTION IN THE GEOMETRIC FORM OF AT LEAST A PART OF A 